#include<stdio.h>
#include<math.h>
int main(void)
{
	int x1,y1,x2,y2,sum;
	while(scanf("%d%d%d%d",&x1,&y1,&x2,&y2)!=EOF)
	{
		sum=abs(x1-x2)+abs(y1-y2);
		printf("%d\n",sum);
	}
	
	return 0;
}

